Oil that sank to the seafloor left a ring the size of Rhode Island

The explosion of Deepwater Horizon oil rig sent an estimated 5 million barrels of oil flowing into the Gulf of Mexico. Most of the oil came to the surface, but about a third of the spill sunk into the depths of the ocean. And, as Mark Schrope writes for Nature News, "Scientists have been trying to locate the missing 2 million barrels since."

Now at least part of that dump has been found: A bathtub ring of oil globs and droplets stains approximately 1,234 square miles of seafloor, researchers report in the Proceedings of the National Academy of Sciences. Deeper regions within the ring contain patches of coagulated oil.

“At a small scale, it’s like a splatter: It landed in small drops, bigger drops, and there may even be some giant drops out there,” study author David Valentine, of the University of California, Santa Barbara, told U.S. News and World Report. “It splattered on the seafloor in such a way that if you took five samples within a few feet of each other, you might see a hundredfold difference in the amount of oil between each other.”

The team analyzed sediment samples for traces of hopane, an oil contaminant that resists degradation. They estimate the ring holds 4 to 31 percent of the approximately 84 million gallons of missing oil. (U.S. oil barrels hold 42 gallons.)

“They are accounting for a significant fraction of the oil that was kind of missing from the budget,” Charles Fisher, a deep-sea biologist at Pennsylvania State in University Park, told Nature News.

In an email, [BP] spokesman Jason Ryan said, "the authors failed to identify the source of the oil, leading them to grossly overstate the amount of residual Macondo oil on the sea floor and the geographic area in which it is found."

Chemical analysis like that would be impossible at that point, Valentine countered. But the patterns they found point to the oil well.

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About Marissa Fessenden

Marissa Fessenden is a freelance science writer and artist who appreciates small things and wide open spaces.

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